The proliferation of mobile devices has been occurring for several years. With this growth has been the increased use of acoustic signal-based communications among both mobile and other types of non-mobile devices. This form of interaction requires that the device has a speaker and a microphone. Another characteristic of this type of device interaction is that the speaker on the device always be on in order to transmit acoustic signals. Existing modulation methods for acoustic based interaction between devices include Amplitude Shift Keying, Frequency Shift Keying, Phase Shift Keying, and Quadrature Amplitude Modulation. All these approaches require continuous non-zero amplitude signals. This leads to high power consumption on the device. Furthermore, many of the devices used in these interactions are mobile or wearable devices, such as smartphones, fitness trackers, and the like, which typically do not have long-lasting power sources.
As noted, wearable devices have also been growing in popularity. For these types of device, extending battery life or, conversely, finding ways to preserve power, is becoming increasingly important. These devices have been interacting with other devices using continuous acoustic-signal based communication. They send inaudible sound signals to other devices which requires that the speaker on the device always be powered on in order for it to be continuous. Similarly, the device microphone (or other signal-detecting component) must always be on in order to detect the signal. These components, especially the speaker needed for transmitting the acoustic signals, are the most energy consuming hardware components on the device. As a result, existing continuous acoustic signal communication solutions between devices are relatively high power consuming operations for the devices.
This is especially an issue with smaller mobile devices where energy efficiency is an important factor. Having a speaker always powered on can quickly drain the battery of a device, which is likely to preclude using acoustic communications for interacting with low-power devices. What is needed is an energy efficient solution to enable continuous and real-time acoustic communication for a variety of devices.